[PATCH 19/24] sys:__sys_setgid(): handle fsid mappings

Christian Brauner christian.brauner at ubuntu.com
Tue Feb 11 16:57:48 UTC 2020


Switch setgid() to lookup fsids in the fsid mappings. If no fsid mappings are
setup the behavior is unchanged, i.e. fsids are looked up in the id mappings.

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 kernel/sys.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index afaec8d46bc5..11f41e0a4974 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -416,24 +416,31 @@ long __sys_setgid(gid_t gid)
 	const struct cred *old;
 	struct cred *new;
 	int retval;
-	kgid_t kgid;
+	kgid_t kgid, kfsgid;
 
 	kgid = make_kgid(ns, gid);
 	if (!gid_valid(kgid))
 		return -EINVAL;
 
+	kfsgid = make_kfsgid(ns, gid);
+	if (!gid_valid(kfsgid))
+		return -EINVAL;
+
 	new = prepare_creds();
 	if (!new)
 		return -ENOMEM;
 	old = current_cred();
 
 	retval = -EPERM;
-	if (ns_capable(old->user_ns, CAP_SETGID))
-		new->gid = new->egid = new->sgid = new->fsgid = kgid;
-	else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid))
-		new->egid = new->fsgid = kgid;
-	else
+	if (ns_capable(old->user_ns, CAP_SETGID)) {
+		new->gid = new->egid = new->sgid = kgid;
+		new->fsgid = kfsgid;
+	} else if (gid_eq(kgid, old->gid) || gid_eq(kgid, old->sgid)) {
+		new->egid = kgid;
+		new->fsgid = kfsgid;
+	} else {
 		goto error;
+	}
 
 	return commit_creds(new);
 
-- 
2.25.0



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